(1) Field of the Invention
This invention relates to highly durable silica glass, and a process and an apparatus for producing the highly durable silica glass. The highly durable silica glass contains a plasma resistance-enhancing element substantially uniformly dispersed therein and exhibits an enhanced resistance to plasma applied in an apparatus using a plasma such as a semiconductor-production apparatus or a liquid crystal-production apparatus.
This invention further relates to a member such as a vessel for a semiconductor, a tool or jig, or a bell jar for a plasma etcher, which member is provided in a semiconductor production apparatus or a liquid crystal production apparatus; and to a semiconductor production apparatus or a liquid crystal production apparatus.
(2) Description of the Related Art
A production apparatus using a plasma is widely used, for example, as a semiconductor production apparatus and a liquid crystal production apparatus. In recent years, there is an increasing importance in a dry etching technique using a plasma along with micro-miniaturization of semiconductor integrated circuits. In the dry etching technique using a plasma, a halogen-containing compound gas such as a fluorine-containing compound gas or a chlorine-containing compound gas must be used. In view of high reactivity, a halogen-containing compound gas and its plasma are widely used, for example, as etching gas for dry etching or as cleaning gas in a thermochemical vapor deposition process. Many kinds of halogen-containing compound gas are used which include, for example, fluorine-containing compound gas such as HF, CF4, CHF3 and NF3, chlorine-containing compound gas such as Cl2, HCl, BCl3 and CCl4, and bromine-containing compound gas such as Br2 and HBr.
In apparatuses using a plasma, such as a semiconductor production apparatus and a liquid crystal production apparatus, a silica glass member is popularly equipped. For example, a bell jar or a focus ring, which is made of transparent silica glass is used. This is because a raw material for silica, i.e., a high-purity quartz powder is not expensive and silica glass is easy to machine and is easily molten by oxyhydrogen flame. Therefore, a shaped high-purity silica glass article having a complicated shape can be produced with a low production cost. Further, silica glass exhibits enhanced high-frequency transmittance.
However, a silica glass member has a problem in durability. That is, when a silica glass member is repeatedly exposed to a halogen-containing compound gas or a plasma thereof, the surface layer thereof is gradually etched and the section thickness to reduced. For example, a fluorine-containing plasma such as CF4/O2 is used, silicon in the silica glass is allowed to react with fluorine radical to form SiF4 which is evaporated. The reduction of section thickness shortens the service life of silica glass member and tends to cause abnormal discharge.
For a member which is exposed to a high temperature such as a flange of a semiconductor-production apparatus, a high-purity opaque silica glass is used because of excellent heat insulation. However, a conventional opaque silica glass has fine bubbles formed therein for enhancing opaqueness and thus, the surface is rough, and the silica glass has poor sealability and poor toughness and exhibits poor impact resistance when it is exposed to plasma etching gas at high temperature.